Grain Growth Behavior and Improved Mathematical Model of a New-Type Superalloy

The grain growth at high temperature significantly affects the ultimate grain sizes and mechanical properties of superalloy. To study the grain growth behavior of a new-type nickel-base superalloy, GH4065 alloy, a series of grain growth tests within the holding temperature range of 1100–1350 K and holding time range of 0–14,400 s were conducted. Via the morphology analysis, it was concluded that the grains of GH4065 alloy normally grow during the temperature range of 1100–1250 K and abnormally grow during the temperature range of 1300–1350 K. The average grain sizes at different experimental conditions were counted and the influences of holding temperature and holding time on the average grain sizes of GH4065 alloy were investigated. It was revealed that the grain sizes increase but the grain growth rates gradually slow down with the increase of holding time; the grain sizes increase with the holding temperature increase and higher temperature further promotes the grain growth degree. Based on the Sellar-type and Anelli-type grain growth mathematics model, an improved two-segment grain growth model was developed and computed to describe the grain growth behavior of GH4065 alloy at high temperature. The evaluation results show that the constructed grain growth model possesses high prediction precision in grain growth behavior characterization of GH4065 alloy.